linux-kernel - Re: [PATCH v2 2/2] ppdev: add support for compat ioctl

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Date:	Wed, 30 Dec 2015 19:18:52 +0530
From:	Sudip Mukherjee <sudipm.mukherjee@...il.com>
To:	Bamvor Jian Zhang <bamvor.zhangjian@...aro.org>
Cc:	Arnd Bergmann <arnd@...db.de>, linux-kernel@...r.kernel.org,
	y2038@...ts.linaro.org, gregkh@...uxfoundation.org,
	broonie@...nel.org
Subject: Re: [PATCH v2 2/2] ppdev: add support for compat ioctl

On Wed, Dec 30, 2015 at 09:24:21PM +0800, Bamvor Jian Zhang wrote:
> Hi, Sudip
> 
> On 12/30/2015 07:16 PM, Sudip Mukherjee wrote:
> > On Fri, Dec 18, 2015 at 12:12:05AM +0100, Arnd Bergmann wrote:
> >> On Thursday 17 December 2015 17:58:52 Bamvor Jian Zhang wrote:
> >>> The arg of ioctl in ppdev is the pointer of integer except the
> >>> timeval in PPSETTIME, PPGETTIME. Different size of timeval
> >>> is already supported by the previous patches. So, it is safe
> >>> to add compat support.
> >>>
> >>> Signed-off-by: Bamvor Jian Zhang <bamvor.zhangjian@...aro.org>
> >>>
> >>
> >> Reviewed-by: Arnd Bergmann <arnd@...db.de>
> >>
> >> (I think I replied with the reviewed-by tag before to this patch)
> > 
> > I was testing this series today. And it is breaking my userspace code. I
> > am attaching my userspace code for you to check. Its very simple
> > userspace code:
> > 1: open
> > 2: ioctl to claim
> > 3: ioctl - PPGETTIME
> > 4: ioctl - PPSETTIME
> > 5: ioctl - PPGETTIME
> > 6: ioctl - release
> > 7: close
> > 
> > Without this series it works as expected.
> > 
> > With this series applied, the userspace code prints the error message:
> > PPNEGOT: Bad address
> > 
> > I traced it with strace and:
> > ioctl(3, PPGETTIME, 0xbfe91508)         = -1 EFAULT (Bad address)
> Thanks for your testing. It seems that I misuse the parameters. Could
> you please apply the following patch and try it again?
> There is no parport in my computer, Thanks.
> 
> diff --git a/drivers/char/ppdev.c b/drivers/char/ppdev.c
> index 31bc7b7..9e98d01 100644
> --- a/drivers/char/ppdev.c
> +++ b/drivers/char/ppdev.c
> @@ -636,7 +636,7 @@ static int pp_do_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
>  		if ((time32[0] < 0) || (time32[1] < 0))
>  			return -EINVAL;
>  
> -		if (copy_to_user(time32, argp, sizeof(time32)))
> +		if (copy_to_user(argp, time32, sizeof(time32)))
>  			return -EFAULT;
>  
>  		return 0;
> @@ -648,7 +648,7 @@ static int pp_do_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
>  		if ((time64[0] < 0) || (time64[1] < 0))
>  			return -EINVAL;
>  
> -		if (copy_to_user(time64, argp, sizeof(time64)))
> +		if (copy_to_user(argp, time64, sizeof(time64)))
>  			return -EFAULT;
>  
>  		return 0;

It works. Tomorrow I will test it on a 64 bit system also.

regards
sudip
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